Early effects of N-acetyl-2-Aminofluorene (AAF), a chemical inducer of rat hepatocarcinogenesis, will be studied on liver cells in vitro. A proliferation-competent primary adult rat hepatocyte culture system that metabolizes AAF, that is highly differentiated and that responds to physiological regulators will be used to characterize the chemical nature of carcinogen binding to DNA. Further attempts will be made to isolate, characterize, and culture putative preneoplastic oval cells. These studies may provide insight into the pathophysiology of chemically-induced epithelial cancer.